Consider that most of the expensive stuff that is known "rare" are something like the army demo Lugers in .45, of which they know less 30 were made, and like 10-15 are located, and the most expensive is serial number 2, the demo piece, as SN 1 was destroyed.
That is rare,
OTH, you have stuff like the garand, m1911, M1911A and the 1903, where the rifle was made in the millions, and a rare copy, only 50-500K were made, compared to the total, Rare and 'desirable'
Compared to something in the 10-1000's made, not rare, but the difference is, the well know rare will sell at the premium, the true rare, is either a curiosity or some unknown 'junk'